La Batalla de las Corrientes: Edison, Tesla y el nacimiento del sistema de potencia

Existe una importante actividad científica conducente a la modernización del sistema eléctrico de potencia y son muchas las nuevas características requeridas en términos de confiabilidad, eficiencia e integración de energías renovables. Sin embargo, es imposible desarrollar las tecnologías necesarias para la evolución del sistema eléctrico sin conocer la historia de su evolución, que ha dado como resultado la arquitectura de sistemas de potencia y distribución eléctrica que tenemos hoy día. Este artículo presenta una reseña histórica de la evolución de los sistemas de suministro eléctrico, hasta llegar al sistema de potencia moderno. Se introducen los eventos más relevantes que dieron forma al sistema eléctrico de corriente alterna, así como los personajes involucrados en este proceso. El artículo inicia con los esfuerzos de Edison para mejorar la bombilla y sus consecuentes desarrollos en sistemas de distribución eléctrica de corriente alterna mediante la Edison General Electric Company. Luego se introduce la figura de Nikola Tesla y su envolvimiento con Edison en sistemas DC. También se mencionan las acciones incurridas por Westinghouse en el sector eléctrico, y que originaron la competencia entre las compañías promotoras de sistemas DC y AC. En ese punto, se presentan los eventos ocurridos durante el periodo conocido como la guerra de las corrientes, los cuales concluyen con las demostraciones exitosas de Westinghouse del sistema de distribución en AC, especialmente en la feria mundial de Chicago de 1893

Design of a Two-Level Boost Converter

The objective of this paper is to demonstrate the design of a two-level boost converter and its controller. First, the context of the importance of such a converter is stablished. Then, the operation of an ideal converter is studied to determine some fundamental relationships necessary for design. Also, the non-idealities of the converter are introduced and a set of equations are developed which are later used to design a converter for a hybrid vehicle application. Finally, various control strategies are studied for the designed converter and implemented in MATLAB/Simulink.The objective of this paper is to demonstrate the design of a two-level boost converter and its controller. First, the context of the importance of such a converter is stablished. Then, the operation of an ideal converter is studied to determine some fundamental relationships necessary for design. Also, the non-idealities of the converter are introduced and a set of equations are developed which are later used to design a converter for a hybrid vehicle application. Finally, various control strategies are studied for the designed converter and implemented in MATLAB/Simulink

Entrevista al Ing. Simón Villa Arango. Innovación Tecnológica en América Latina

Simón Villa es un científico innovador, colombiano - paisa, nacido en la ciudad de Medellín. Su formación profesional lo ha llevado de Colombia, donde obtuvo su grado como ingeniero biomédico en la Universidad EIA en colaboración con la Universidad CES, a Inglaterra, donde realiza un doctorado en ingeniería biomédica en el área de pruebas cerca al paciente con City, University of London, de vuelta a Colombia, donde luego de un par de años trabajando en investigación fundó la incubadora de patentes y tecnologías - Incubba y donde actualmente se desempeña como jefe de innovación tecnológica de la Universidad EIA

Entrevista con el Dr. Mehrdad Ehsani

El Dr. Mehrdad Ehsani es profesor del Departamento de Ingeniería Eléctrica, director del Laboratorio de Electrónica de Potencia y Sistemas de Propulsión Eléctrica y director del Programa de Energía Sostenible e Ingeniería Vehicular en la Universidad de Texas A&M. En el mes de junio del 2012, el Dr. Ehsani estuvo en la Ciudad de Panamá participando en el proyecto “Estudio de Alternativas Energéticas Sostenibles para Panamá” y aprovechamos esta oportunidad para entrevistarlo

Stochastic modeling of the variation of velocity and permeability as a function of effective pressure using the Bed-of-Nails asperity-deformation model

The mechanical and transport properties of porous and cracked media, such as velocity and permeability, are sensitive to the effects of effective pressure, which itself is a function of the confining pressure and the pore-fluid pressure. The dependence of permeability and velocity on effective pressure has previously been modeled using the Bed-of-Nails asperity-deformation model. The main objective of this research was to explore the sensitivity of the Bed-of-Nails and effective-pressure models to random, Gaussian errors, by using an inverse approach. To achieve this, numerical modeling of pre-existing velocity and permeability experimental data sets was done. Extrapolation to 600 MPa was performed using an epidosite data set of compressional velocity as a function of confining pressure, only using measurements in the range 0-100 MPa. The results showed that, given sufficient data and considering random error only, extrapolation can be done with a level of error of less than 1.5%. Model error can also be significant in this type of exercise because it can give rise to systematic misfit, although in this case it was shown that the effects of model error were not considerable. Modeling the variation of compressional velocities as a function of confining and pore-fluid pressures in a deep-sea chalk showed that the best-fitting asperity-deformation model is sensitive to the effective-pressure model. Measurements of permeability in a Navajo-sandstone specimen as a function of confining pressure were numerically modeled, and the results showed that measurements made at low pressures, specifically near Pe = 0, are very important to constrain the model. The same result was found in the case of permeability as a function of confining and pore-fluid pressure in a Wilcox-shale where the lack of measurements near Pe = 0 caused the error in the model parameters to be overestimated. This occurs because the rate of change of permeability as a function of effective pressure is very high at low pressures. The lack of sufficient data near Pe = 0 overestimates the curvature matrix and, therefore, the errors in the model parameters

Editorial : Pathophysiology and treatment of fusiform intracranial aneurysms

Non peer reviewe

Contralateral approach to anterior circulation aneurysms

Objective Multiple intracranial aneurysms are frequent, with an incidence of 15-40% among intracranial aneurysms carriers. Of these carriers, 20-40% have bilateral intracranial aneurysms. The rupture risk is higher for patients with multiple intracranial aneurysms. For those patients, several treatment options are available (microsurgery comprising a unilateral-contralateral approach, bilateral craniotomies in one-stage or two stages surgery, and endovascular methods) varying from institution s resources and surgeon s experience. The present study focuses and analyses the angiographic characteristics, specific parameters, and surgical results of the unilateral-contralateral approach for ICA-opht segment and MCA aneurysms. In addition, it describes and analyses the proximal vascular control by transient cardiac arrest induced by adenosine during the contralateral clipping of ICA-opht segment aneurysms. Patients and Methods We retrospectively reviewed 68 patients with ICA-opht segment and bMCA aneurysms treated through a contralateral approach at the department of neurosurgery of the University of Helsinki, between January 1998 and December 2013. A detailed analyses of the aneurysms characteristics and constrains of the contralateral surgical corridor was performed. A further subgroup analysis of 8 patients harboring ICA-opht segment aneurysms approached through a contralateral craniotomy and requiring intravenous adenosine administration to induce transient cardiac arrest during microsurgical clipping was performed as well. Results ICA-opht segment aneurysms: All the 30 ICA-opth aneurysms were small (less than 7 mm), unruptured, saccular, and had no wall irregularities, calcifications or secondary pouches. Microsurgical clipping of these aneurysms was possible when the prechiasmatic distance had a median of 5.7 mm (range 3.4-8.7 mm) and the interoptic distance a median of 10.5 mm (range, 7.6-15.9). The most frequent aneurysm dome projection was superomedial (77%). Of the patients with ICA-opht segment aneurysms approached through a contralateral craniotomy, 93% had good postoperative outcome at 3-month follow-up. bMCA aneurysms: The contralateral approach for bMCA aneurysms was possible in 38 patients. All the 38 contralaterally approached MCA aneurysms were unruptured and had saccular shape (expect one with bilobular shape). The majority (97%) of contralateral aneurysms were small to medium in size. The median length of the contralateral A1 was 13.2 mm (range: 6-19.8 mm), and the median length of the contralateral M1 was 14.2 mm (range: 4.6-21 mm). Of the patients with unruptured bMCA aneurysms treated through a contralateral approach, 24 (86%) patients had good outcome and 4 (14%) had poor outcome at 3-month follow-up, 1 patient was lost to follow-up. There were 9 patients harboring bMCA aneurysm presented with SAH due to a ruptured ipsilateral aneurysm. Of these patients, 7 (78%) had good outcomes, and 2 (22%) had poor outcomes at 3 months. Olfactory disturbances were present in 21% of cases treated through a contralateral approach. Transient cardiac arrest induced by adenosine during contralateral clipping of ICA-opht aneurysms: 8 patients received intravenous bolus of adenosine to induce transient cardiac arrest during clipping. Of the total patients, 5 received single bolus of adenosine, and 3 patients received multiple doses. The median single dose of adenosine was 22.5 mg (range, 5-50 mg). The asystole time range between 20-40 seconds after adenosine administration. All the 8 patients showed good surgical outcomes at 3-month and 1-year follow-up, and showed no procedure-related complications. Conclusion: The contralateral approach remains as a feasible option for microsurgical treatment of ICA-opht segment aneurysms, and bMCA aneurysms. Its feasibility depends on general parameters related to the aneurysm itself (shape, morphology, size, status and projection), and specific parameters that varies according to the vascular segment to be treated (prechiasmatic and interoptic distances, length of A1 and M1). Transient cardiac arrest induced adenosine represents a useful tool to obtain proximal vascular control while performing a contralateral approach for ICA-opth segment aneurysms in selected patients.Johdanto Multippelien kallonsisäisten aneurysmien esiintyvyys on 15-40% kaikista aneurysma-potilaista. 20-40% aneurysmat ovat molemminpuoliset. Aneurysman puhkeamisen riski on niillä potilailla, joilla multippelit aneurysmat. Multippeli aneurysmat voidaan hoitaa mikrokirurgisesti klipsamalla unilateraalisen tai bilateraalisen kraniotomian kautta tai endovaskulaarisesti täyttämällä aneurysmat. Meidän tutkimuksessa on analysoitu multippeleita ICA-oftalmika (ICA-oft) ja MCA aneurysmien kuvantamisominaisuuksia ja mikrokirurgisen hoidon tuloksia riippuen lähestymistavasta. Lisäksi tutkimuksessa analysoitiin adenosiinilla väliaikaisen sydämen- ja verenkiertopysähdyksen käyttöä ICA-oftalmica aneurysmien leikkauksissa. Aineisto Olemme retrospektiivisesti analysoineet 68 potilaan ICA-oft ja bilateraali MCA (bMCA) aneurysmat, jotka hoidettiin HYKS Neurokirurgian klinikassa vv. 1998-2013. Aneurysmien ominaisuudet ja kirurgisen lähestymistavan nyansseja on myös analysoitu. Erikseen olemme katsoneet läpi ryhmä ne ICA-oft aneurysmapotilaita (n=8), jolla aneurysman klipsaus oli tehty vastakkaiselta puolelta käyttäen intraoperatiivista sydämen-ja verenkiertopysähdystä adenosiinilla. Tulokset ICA-oft aneurysmat: Kaikki aneurysmat olivat pienkokoisia (halkaisija alle 7 mm), vuotamattomia, sakkularisia, ilman seinämän epätasaisuuksia tai kalkkeumia. Aneurysman mikrokirurginen klipsaus oli mahdollinen jos prekiasmaattinen etäisyys oli 5,7 mm (3,4-8,7) ja interoptinen etäisyys oli 10,5 mm (7,6-15,9). Useimmiten anurysma suuntautui superomediaalisesti (77%). Kolmen kuukauden kontrollissa ICA-oft aneurysman kontralateraaliklipsauksen tulokset oli hyviä 93%:lla potilaista bMCA-aneurysmat: Tässä ryhmässä kontralateraaliklipsaus oli sopiva 38 potilailla. Kaikissa tapauksissa aneurysma oli vuotamaton ja sakkularinen. Suurin osa (97%) näistä aneurysmista oli pieniä tai keskikokoisia. Kontralateraali A1 segmentin mediaani pituus oli 13,2 mm (6-19) ja kontralateraali M1 segmentin mediaani pituus oli 14,2 mm (4,6-21). bMCA-aneurysmien ryhmässä kontralateraaliklipsauksen tulokset 3 kk kontrollissa oli hyviä 24 (86%) potilaalla ja huonoja 4 (14%) potilaalla. Hajuaistin ongelmat ovat tulleet esille 21%:lla potilaista. Väliaikainen sydämen pysähdys adenosiinilla ICA-oft aneurysman leikkauksessa: Tämä menetelmä on käytetty kahdeksalla potilaalla. Viisi heistä saivat yhden boluksen adenosiinia ja kolmelle annettiin tätä lääkettä toistetusti. Adenosiinin mediaani annos oli 22,5 mg (5-50mg). Sydämen pysähdys kesti 20-40 sek. Kolmen kuukauden kontrollissa kaikilla potilaalla tässä ryhmässä oli hyvät tulokset eikä todettu adenosiiniin liittyviä komplikaatiota. Johtopäätökset: Kontralateraali lähestyminen soveltuu osaan ICA-oft ja bMCA aneurysmien hoitoon. Soveltuminen kontralateraaliseen lähestymiseen riippuu aneuryman morfologisista ominaisuuksista ja verisuonen etäisyydestä kriittisiin alueisiin ja kallonpohjan anatomiasta (prekiasmaattinen, interoptinen etäisyys, A1 ja M1 pituus). Väliaikainen sydämen pysähdys adenosiinilla sallii proksimaalisen kontrollin ICA-oft aneurysmaleikkauksessa kontralateraaliavauksen aikana

Characteristics of students competent in the use of ICT, tenth grade of the average level in Colombia

La presente investigación tiene como objetivo principal determinar las características que poseen los estudiantes competentes en el uso de las TIC en el grado décimo del nivel media, de una institución educativa en la ciudad de Montería en Colombia. Para ello, se revisaron las competencias que se desarrollan en la Institución, las estrategias que implementan los docentes para dicho proceso y a modo de comparación, se establecieron las dificultades que presentan tanto los estudiantes competentes, como los que no lo son en ese ámbito. Este estudio está orientado por un enfoque mixto con un estatus equitativo y de naturaleza secuencial para el desarrollo de dos etapas, una cualitativa a través de un método de casos múltiples, en la cual se realizaron entrevistas a seis alumnos y tres docentes; y una cuantitativa, donde se aplicó una encuesta con escala tipo Likert a cincuenta estudiantes. Los principales hallazgos indican que los estudiantes se caracterizan por el desarrollo de competencias en el manejo de dispositivos tecnológicos y de programas de aplicación; en la búsqueda, organización y análisis de información; en la comunicación y colaboración y también, demuestran una actitud positiva ante el uso de las TIC. Así mismo, se encontró que los docentes implementan metodologías con el fin de fortalecer el desarrollo de las competencias en el uso de las TIC, la comunicación entre docente-estudiante y el trabajo colaborativo. Por último, se pudo determinar que las principales deficiencias que presentan los alumnos en su desarrollo de la competencia en el uso de las TIC se centran en los conocimientos y operación de las mismas, en el manejo de información, en el trabajo colaborativo en línea y en el respeto a la propiedad intelectual de otros.Instituto Tecnológico de Estudios Superiores de Monterrey ITESM1. Planteamiento del problema.................................................................................... 1 1.1. Antecedentes................................................................................................... 2 1.2. Definición del problema.................................................................................. 6 1.3. Objetivos......................................................................................................... 8 1.3.1. Objetivo General..................................................................................... 9 1.3.2. Objetivos Específicos.............................................................................. 9 1.4. Justificación.................................................................................................... 10 1.5. Limitaciones y delimitaciones........................................................................ 15 2. Marco teórico.......................................................................................................... 18 2.1 Mapa de conceptos claves................................................................................ 19 2.2. Definición del concepto de competencia........................................................ 20 2.3. Competencias transversales en la educación.................................................. 22 2.4. Competencia en el uso de TIC........................................................................ 26 2.4.1. Competencias TIC de acuerdo con algunos organismos internacionales 29 2.4.2. Dimensiones de la competencia en el uso de TIC................................... 32 2.4.3. Características de una persona competente en el uso de TIC.................. 36 2.5. Políticas relacionadas con el uso de las TIC en la educación......................... 42 2.6. Pruebas Saber 9º.............................................................................................. 45 2.7. Teoría de principiantes y expertos.................................................................. 48 3. Método.................................................................................................................... 54 3.1. Propuesta metodológica.................................................................................. 55 3.2. Marco contextual............................................................................................. 58 3.3. Etapa 1: aproximación cualitativa................................................................... 61 3.3.1. Participantes............................................................................................ 63 3.3.2. Instrumentos............................................................................................ 64 3.3.3. Procedimiento de colección de datos...................................................... 65 3.3.4. Procedimiento de análisis de datos.......................................................... 66 3.4. Etapa 2: aproximación cuantitativa................................................................. 67 3.4.1. Participantes............................................................................................ 69 3.4.2. Instrumentos............................................................................................ 70 3.4.3. Procedimiento de colección de datos...................................................... 71 3.4.4. Procedimiento de análisis de datos.......................................................... 72 4. Análisis y discusión de resultados.......................................................................... 73 4.1. Etapa 1: análisis de datos cualitativos............................................................. 73 4.1.1. Categoría 1: Competencias TIC en el grado décimo............................... 74 4.1.1.1. Conocimientos, operación y uso de sistemas informáticos............. 74 4.1.1.2. Investigación y manejo de información........................................... 76 4.1.1.3. Comunicación efectiva y colaboración............................................ 79 4.1.1.4. Ética y convivencia digital.............................................................. 81 4.1.2. Categoría 2: Características generales..................................................... 83 4.1.3. Categoría 3: Metodología de los docentes.............................................. 87 4.1.4. Categoría 4: Desempeño en Pruebas Saber............................................. 92 4.1.5. Categoría 5: Carencias formativas en el uso de TIC............................... 95 4.2. Etapa 2: análisis de datos cuantitativos........................................................... 99 4.2.1. Análisis descriptivo................................................................................. 100 4.2.2. Análisis psicométrico.............................................................................. 117 4.2.3. Análisis de relaciones.............................................................................. 121 4.3. Discusión de resultados en función a las preguntas de investigación............. 123 5. Conclusiones........................................................................................................... 136 5.1. Alcances y limitaciones del estudio................................................................ 143 5.2. Recomendaciones para futuros estudios........................................................ 145 Referencias.................................................................................................................. 147 Apéndices.................................................................................................................... 155 Apéndice A. Cartas de consentimiento....................................................................... 155 Apéndice B. Entrevista de la etapa cualitativa dirigida a estudiantes........................ 157 Apéndice C. Entrevista de la etapa cualitativa dirigida a docentes............................ 159 Apéndice D. Encuesta de la etapa cuantitativa dirigida a estudiantes........................ 161 Currículum Vitae........................................................................................................ 167MaestríaThis research has as main objective to determine the Characteristics that competent students have in the use of information technology and communications in tenth grade students of average level in a school of Monteria Colombia. In order to, were reviewed the competences developed in the institution, the strategies which teachers implement for such development and for a comparison way, there were established the difficulties presented by both competent students, as they are not in this area. This study is guided by a mixed approach with an equal status and sequential nature to the development of two stages, a qualitative method through a multiple cases, in which six students and three teachers were interviewed and a quantitative, where a survey was conducted by a Likert type scale to fifty students. The principals findings indicate that students are characterized by the development of competences in the management of technological devices, and application program; in finding, organizing and analyzing information; in communication and collaboration, Also demonstrate a positive attitude towards the use of ICT . Also, it was found that teachers implement methodologies to strengthen the development of competences in the use of ICT, the communication between teacher-student and a collaborative work.Modalidad Presencia

Investigation of Multi-Frequency Power Transmission and System

This dissertation presents a new power system transmission concept based on frequency selectivity named Multi-Frequency Power System (MFPS). This system allows for selective power transmission among terminals in an interconnected system, and is enabled by power electronic technology. The dissertation starts with a presentation of some of the challenges faced by modern power systems, and includes a description of various power system technologies developed in an attempt to solve them. Then, our proposed solution is presented as an alternative to electric power transmission, and the fundamental concepts are explained. A version of the MFPS is developed, which has relevance to the problem of renewable sources integration. This AC DC Power System is further explored, and the topology of the system and the converters is presented, as well as the control techniques used in its operation. The dissertation also presents a performance study of the AC DC system, which was done in Simulink, and it demonstrates the robustness of the system under various dynamic and fault conditions. Finally, a summary of the work is given in the last section of the dissertation. The contributions of our research to the state of technology are discussed. These contributions include: the demonstration of power selectivity based on frequency identification, the development of a novel transmission system and a AC DC integrated implementation of it, and the development of a control and converter that enables selective power transmission. Also, some of the most relevant future research initiatives related to this topic are presented